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Tribe Travail (Posted on 2014-01-21) Difficulty: 3 of 5
On a certain island, there are three tribes - the Whites, the Oranges, and the Lemons which have different standards of veracity. It is not possible to distinguish them otherwise.
Whites are the knights who always tell the truth; Oranges are the liars who always speak falsely. Lemons are knaves who tell the truth and lie alternately, albeit not necessarily in this order.

A visitor was somewhat confused recently when he was introduced to three natives named Mr. White, Mr. Orange, and Mr. Lemon, who belong to the White tribe, the Orange tribe, and the Lemon tribe - albeit not necessarily in this order. There was also a fourth native named Mr.Yellow.

The visitor asked each of the first three natives (a) what his own tribe was, and (b) what was Mr. Yellow's tribe. To these questions, the responses of the three natives was as follows:

Mr. White replied: "I'm not a White. Mr. Yellow is an Orange."
Mr. Orange replied: "I'm not an Orange. Mr. Yellow is a Lemon."
Mr. Lemon replied: "I'm not a Lemon. Mr. Yellow is a White."

To which tribe does Mr. Yellow actually belong?

No Solution Yet Submitted by K Sengupta    
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Question Analytical Solution (spoiler) | Comment 2 of 3 |
The Orange liar cannot say "I'm not a White" or "I'm not an Lemon", so Mr. Orange must be the Orange liar.

The White knight cannot say "I'm not a White", so Mr. White is not a knight.  And we have already determined that Mr. Orange is not the knight.  Therefore, Mr. Lemon must be the knight.

And since Mr. Lemon only makes true statements, Mr. Yellow is a White.

  Posted by Steve Herman on 2014-01-21 22:42:41
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